Monopterus albus - Asian Swamp Eel

Information Last Reviewed Spring 2007

Significant adverse impacts have yet to be documented, but due to their predatory nature, Asian swamp eels appear to have the potential for adverse environmental impacts in North America. There is concern, for example, that they may disrupt the Everglades National Park ecosystem.

Swamp eels are not true eels (order Anguilliformes). True eels have scales, dorsal, anal and caudal fins, and functioning pectoral fins. True eels have two gill openings and the gill membranes are not united. An obvious difference between the two groups is that anguilliform eels have distinctive, planktonic larvae that are thin, transparent, and can be quite large and leaf-like in appearance. As such, the Anguilliformes is a group of fish with largely ancestral characteristics and placed in the teleost infradivision Elopomorpha. Swamp eels have mostly derived characteristics and are placed in the infradivision Eutelostei and are percomorphs.

Distinguishing Characteristics

Scaleless, elongated body with a tapering tail and blunt snout

Teeth appear like bristles

One V-shaped gill located beneath the head

May be mistaken for native American eel (Anguilla rostrata), except that American eel have pectoral fins, rayed dorsal, anal and caudal fins, and scales (although embedded).

May be mistaken for lamprey, but these latter fish have no jaws and have ovoid mouths; lampreys also have distinct dorsal and caudal fins and seven gill openings on each side. (Fig. 1)

General Biology:

Morphology

Body is cylindrical with the tail compressed and tapering to a point (Fig. 2)